It's a fun exercise to divide the replacement cost by your estimate of the items useful life to calc out how much you should theoretically have in your reserve fund each year.I'm a long ways from theoretical, but at least I know how far off I am.Best to you.

I'm purchasing a home and the lender has sent me over the estimated closing costs.

Maybe save that for when you have accumulated some serious equity and plant roots there?

For example, we typically fund between 70-80% of the Purchase price in addition to 100% of the rehab estimate for our Fix n Flip loans.

I Have a 3BR 2ba 1500 square feet house under contract for $59,900 and a estimate repair cost between $20000-$25000.

So far her has received 2 estimates. $800(IMO too low) and $6100(IMO way too high).

As you accumulate more properties, you end up with central AC units of all sizes and ages.Many of these require odd size filters you can't buy at the big box stores, so what do you do? 

Besides calling a general inspector to check for obvious issues, and a general contractor for estimating rehab costs, is there anything else I can do to reduce exposure?

The Book on Flipping Houses and The Book on Estimating Rehab Costs.

I estimated 22K for all of the repairs and upgrades using the high estimates provided by Homewyse Here are the numbers: Taxes $3,000Insurance $1,500 estimatedVacancy $1,400 one monthLawn care $600Misc  $1,000Comp rents for he area are about $1,495 but I am estimating $1,400 to be safe.What do you think?